首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   41494篇
  免费   1541篇
  国内免费   11篇
  2019年   444篇
  2018年   646篇
  2017年   604篇
  2016年   690篇
  2015年   510篇
  2014年   600篇
  2013年   3890篇
  2012年   1051篇
  2011年   1099篇
  2010年   702篇
  2009年   664篇
  2008年   996篇
  2007年   892篇
  2006年   840篇
  2005年   706篇
  2004年   681篇
  2003年   714篇
  2002年   691篇
  2001年   1329篇
  2000年   1285篇
  1999年   990篇
  1996年   531篇
  1995年   495篇
  1994年   487篇
  1993年   478篇
  1992年   977篇
  1991年   893篇
  1990年   893篇
  1989年   780篇
  1988年   778篇
  1987年   775篇
  1986年   772篇
  1985年   763篇
  1984年   675篇
  1983年   557篇
  1982年   435篇
  1981年   458篇
  1979年   657篇
  1978年   473篇
  1976年   436篇
  1975年   590篇
  1974年   605篇
  1973年   659篇
  1972年   624篇
  1971年   556篇
  1970年   504篇
  1969年   497篇
  1968年   597篇
  1967年   532篇
  1966年   490篇
排序方式: 共有10000条查询结果,搜索用时 46 毫秒
921.
922.
The concepts of informed consent and surveillance of human research designed to protect human subjects is commendable. The regulations of the Institutional Review Board (IRB) are having a major impact on clinical cancer research. There is greater administrative time needed of the investigator, the mechanisms of patient care have become cumbersome and some patients reject optional medical management that could be life saving. IRB regulations must be flexible to meet the needs of human subjects as well as those of the clinical investigator.  相似文献   
923.
This article describes three kinds of information constraints in medical encounters that have not been discussed at length in the medical ethics literature: constraints from the concept of a disease, from the diffusion of medical innovation, and from withholding information. It describes how these limit the reliance rational people can justifiably put in their doctors, and even the reliance doctors can have on their own advice. It notes the implications of these constraints for the value of informed consent, identifies several procedural steps that could increase the value of the latter and improve diffusion of innovation, and argues that recognition of these constraints should lead us to devise protections which intrude on but can improve these encounters.  相似文献   
924.
Prior surgical implantation of a venous catheter sensitized rats to coldimmobilization stress. Three of six catheterized females succumbed during the stress. The remaining rats fell into two groups in terms of their core temperature at the end of the stress period: Male uncatheterized rats had higher temperatures than rats in the other three groups. No relation was found between catheter patency and magnitude of hypothermia. Degree of gastric disease paralleled the core temperature findings in that the male uncatheterized rats had significantly fewer gastric erosions than the rats in the other three groups. Additionally, a robust effect of gender was found with uncatheterized females showing more hypothermia and more gastric disease than uncatheterized males. A subsequent experiment was conducted to evaluate whether anesthesia or wearing the protective spring was responsible in part for the sensitization seen. Here, the gender difference was less although females consistently averaged lower core temperatures after stress than did males. Despite similar core temperatures after stress, females that were prepared with the protective spring apparatus developed more gastric disease than female controls or similarly treated males. Thus, the additional sensitization exhibited by females in the first experiment may relate to the fact that both catheterization and the taping procedure were sensitizers while only catheterization was a sensitizer for males.  相似文献   
925.
D McDermott 《Adolescence》1984,19(73):89-97
The purpose of this study was to examine the relationship of two variables, parental drug use and parental attitude toward adolescent drug use, both as perceived by the adolescent respondent to his or her own use or nonuse of drugs. A sample of 106 drug-using and 96 nondrug-using adolescents was obtained through the use of the anthropological " snowball " technique. All respondents were administered a drug use history profile and a personal data questionnaire. In order to be classed as drug users, respondents had to have been using two or more recreational substances on a regular basis. Nondrug users were those who used no recreational drugs, although individuals who had tried alcohol or tobacco experimentally were included in this group. On the personal data form, respondents were asked to describe their parents' use of alcohol, tobacco, or other substances, and to indicate their parents' attitudes concerning adolescent use of drugs. Parental attitudes were classed as permissive if the respondent indicated that parents were indifferent about drug use, if they accepted a certain range of drugs, or if the decision were left up to the youth. A nonpermissive attitude was defined as one which would not accept drug use by the adolescent. Four 2 x 2 Chi-square analyses were used to determine significance of the relationship between adolescent drug use and parents' use or nonuse of drugs, parents' attitudes about adolescent use or nonuse and actual adolescent use or non-use, and this same attitudinal relationship looking at parent users and nonusers separately.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   
926.
D Klein  P Belcastro  R Gold 《Adolescence》1984,19(76):805-815
Several inherent limitations to secondary school sex education program evaluations are: limited generalizability, lack of longitudinal research, and no clear consensus of program outcomes. With a Bureau of Health Education, Center for Disease Control study as the criterion for program outcomes, a study was undertaken to examine the immediate and long-term impact of sex education upon program participants. Two of the 20 schools in the CDC study identified as having exemplary sex education programs provided access to their students and alumni. Inventories which measured perceived achievement of 33 sex education outcomes were piloted for reliability and validity. Each inventory examined participant changes in knowledge, understanding of self, values, interaction skills, self-esteem, and fear of sex-related activities. Students were surveyed in school; alumni were surveyed through the mail. Response rates ranged from 30 to 100 percent for students and alumni at both schools. Overall there was no statistically significant difference between the perceptions of students and alumni as to achievement of investigated outcomes. Alumni responses at one school did, however, indicate some potentially weak areas of their school's program with respect to values and interaction skills outcomes. It appears that program impact may decrease with time. Thus, isolating and addressing the factors involved may be necessary. This would assist program planners and instructors to strengthen curricula and program activities in order to enhance the overall impact of sex education. The present study supports the notion that positive gains are achieved as a result of each school's sex education program, and these gains remained over time.  相似文献   
927.
This study provides a reexamination of the role of different decisional strategies in facilitating progress in occupational decision making. Although the assumptions that a rational decision making style is the preferred mode of vocational functioning has been endorsed in a variety of career theories and interventions, there has been conflicting evidence about the validity of this assumption. To examine the role of different decisional approaches in the progress of making an occupational decision, the rational, intuitive, and dependent decision making style scores of 71 undergraduate students were used to predict progress in occupational decision making. The results of the regression analyses failed to provide support for the assumption that a rational style is the most effective in accomplishing this careerrelated task, but indicated strong support for the conclusion that the use of dependent decisional strategies is damaging, particularly in early stages of the decisional process.  相似文献   
928.
The authors recently proposed that adverse effects of material rewards on Wechsler subscale performance may be the result of a reward-produced developmental regression. The present study further explores that idea through an attempt to replicate earlier findings with adults and to extend the inquiry to children. Selected Wechsler subscales were administered to 32 subjects at each of three ages (5, 10, and 18 years) under either reward or nonreward conditions. Subscales were chosen to represent both algorithmic and heuristic types of tasks. Reward and nonreward groups (8 males and 8 females per group at each age) were matched initially on age and ability. For adults, consistent with earlier findings, reward had an adverse effect on performance on the heuristic subscales and tended to facilitate performance on the algorithmic subscales. However, rewards generally had no effect at the fourth-grade level and had a reverse effect at the nursery school level, i.e., rewards facilitated heuristic and hampered algorithmic performance. These findings appear to be more consistent with an explanation based on developmental regression than on any available alternative mechanism.  相似文献   
929.
930.
Psychology seeks to justify its claims to privilege as a social institution largely on the basis of its scientific knowledge claims. These knowledge claims tend to be based on, and to reflect a particular view about the nature of science which is under increasing challenge. This situation is discussed and some of its implications examined.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号